A composite polymer based on vinylogous urethane vitrimer bonding with both photodimerizable and thermally exchangeable functionalities is described. Polymers containing various ratios of photodimerizable diaminoanthracene monomers and thermally exchangeable diaminoalkyl monomers linked by a common bisacetoacetate group are studied. It is demonstrated that alkyl amines undergo the necessary thermal exchange reactions for vinylogous urethane vitrimers, while aromatic amines do not. UV-induced dimerization of the anthracene units results in changes to the rheological properties and the glass transition temperature due to polymer cross-linking. Rapid and near-complete scratch healing upon heating is demonstrated, with a tunable onset temperature for healing controlled by UV irradiation. The viability of a composite vitrimeric system, wherein vitrimeric monomers are combined with non-vitrimeric, stimuli-responsive monomers to generate random copolymers with new properties, is demonstrated.

Small, red Fe2 SeO single crystals in two modifications were obtained from a CsCl flux. The metastable α-phase is pseudo-tetragonal (Cmce, a=16.4492(8) Å, b=11.1392(4) Å, c=11.1392(4) Å), whereas the β-phase is trigonal (P31 , a=9.8349(4) Å, c=6.9591(4) Å)) and thermodynamically stable within a narrow temperature range. Both crystal structures were solved from twinned specimens. The enantiomers of the β-phase appear as racemic mixtures. Selenium and oxygen form two individual interpenetrating primitive cubic lattices, giving a bcc packing. A quasi-octahedrally coordinated iron atom is found close to the center of each surface of the selenium sublattice. The difference between the α- and β-phases is the distribution of iron at 2/3 of the surfaces. α- and β-Fe2 SeO are comparable with metal-vacancy-ordered antiperovskites. Each Fe/O lattice can also be described in terms of vertex-sharing OFe4 tetrahedra, with a crystal structure similar to that of an antisilicate. Iron is divalent and has a high-spin d(6) (S=2) configuration. The β-phase exhibits magnetoelectric coupling.

Photo-cross-linking of polymeric materials generally requires an inert atmosphere because of oxygen-based inhibition and quenching of the reactive species. Here, we demonstrate the photo-oxidative cross-linking of aminefunctionalized poly(dimethylsiloxane) using atmospheric oxygen as the chemical oxidant. Visible light irradiation of a metalloporphyrin or an organic sensitizer generates reactive singlet oxygen that oxidatively couples amines into imine crosslinks. This facile benchtop cross-linking reaction proceeds at room temperature and results in solvent-free elastic materials after 1 h. Solid state 13 C nuclear magnetic resonance and Fourier transform infrared spectroscopy show that the reaction produces only imine functionalities with no side products observed. The mechanical properties of these polymers were tested using tensile experiments and were found to depend on the initial loading of the sensitizer, with a maximum elongation strain of 157% and a Young's modulus of 2.15 MPa for the highest tested amount. Photolithography is demonstrated with this cross-linking system using visible light irradiation.

The development of low-cost, non-toxic, scalable antimicrobial textiles is needed to address the spread of deadly pathogens. Here, we report a polysiloxane textile coating that possesses two modes of antimicrobial inactivation, passive contact inactivation through amine/imine functionalities and active photodynamic inactivation through the generation of reactive oxygen species (ROS). This material can be coated and cross-linked onto natural and synthetic textiles through a simple soak procedure, followed by UV cure to afford materials exhibiting no aqueous leaching and only minimal leaching in organic solvents. This coating minimally impacts the mechanical properties of the fabric while also imparting hydrophobicity. Passive inactivation of Escherichia coli ( E. coli ) and methicillin-resistant Staphylococcus aureus (MRSA) is achieved with >98% inactivation after 24 h, with a 23× and 3× inactivation rate increase against E. coli and MRSA, respectively, when green light is used to generate ROS. Up to 90% decrease in the infectivity of SARS-CoV-2 after 2 h of irradiated incubation with the material is demonstrated. These results show that modifying textiles with dual-functional polymers results in robust and highly antimicrobial materials that are expected to find widespread use in combating the spread of deadly pathogens.

Millimeter sized polymer crystallites grow rapidly when anthracene-containing siloxanes are photocrosslinked using UV light.